Filter vial

Abstract

A filter vial and piston are provided where the vial has a cylindrical wall with a closed bottom and open top and with the hollow, tubular piston therein. The piston has a distal end covered by a cup having a proximal cup seal extending outward to engage the walls of the vial to form a fluid tight seal with the vial during use. The distal end of the piston has a piston flange extending outwardly and located adjacent a recess in the piston so the cup forms a snap fit over the piston flange and extends into the recess. The piston flange causes the cup to bulge sufficiently outward to form a fluid tight seal with the vial during use. A filter is placed in the bottom of the cup and abuts an inwardly extending lip on the cup. The filter is held against the lip by a piston support at the distal end of the piston. A cup support at a distal end of the cup also helps support the filter.

What is claimed is: 
     
       1. A method of manufacturing a filter vial kit, comprising:
 forming a plastic tube with a closed bottom, an open top and a cylindrical interior wall with a diameter D, the tube having longitudinal axis; 
 forming a tubular, plastic piston having a cylindrical wall defining an interior, forming an outer wall of the piston to have an outer diameter less than D, the tubular piston having a longitudinal axis, forming a distal piston flange at or adjacent to the distal end of the piston with the flange extending outward from the piston and outward from the longitudinal axis of the piston, the piston having distal and proximal ends with the forming step including forming an opening in the distal end of the piston and further forming a filter support at the distal end of the piston extending across that opening, the filter support not blocking that opening and having passages through which fluid can flow through the opening and into the interior of the piston during use; 
 forming a plastic retainer cup having a bottom and continuous sidewall with the sidewall extending between the bottom at a distal end of the cup and a proximal end of the cup, forming the cup sidewall to have an interior diameter sufficiently smaller than the distal piston flange to allow the sidewall to contact but pass over the distal piston flange, forming the cup bottom with at least one opening through which fluid can flow during use, forming on the cup a cup seal extending outward from the proximal end of the cup a distance greater than the diameter D, forming the sidewall of the cup sufficiently flexible to deform outward as the cup passes over the distal piston flange so the sidewall can have an outer dimension larger than diameter D at the location of the piston flange when the retainer cup passes over the distal piston flange; and 
 providing a filter that is configured to fit between and be held between the retaining cup and the distal end of the piston when the proximal end of the retainer cup is placed over the distal end of the piston, the filter being selected to filter fluid passing into the piston during use. 
 
     
     
       2. The method of  claim 1 , further comprising making the vial of a material selected from the group comprising polyolefin, preferably polypropylene, polytetrafluroethylene, polyamid, polyvinyldifloride and polyethersulphone. 
     
     
       3. The method of  claim 1 , wherein the filter support is formed inside the piston. 
     
     
       4. The method of  claim 1 , further comprising forming on the cup a cup lip extending inward toward a longitudinal axis of the cup at the distal end of the retainer cup lip so the cup lip extends a distance sufficient to stop passage of the filter along the longitudinal axis of the cup. 
     
     
       5. The method of  claim 1 , further comprising forming the distal end of the piston with an outward facing wall having a recessed area therein extending entirely around a circumference of the piston. 
     
     
       6. The method of  claim 5 , further comprising configuring the cup relative to the recessed area so the cup seal may be located in the recessed area when the cup is placed over the distal end of the piston for use. 
     
     
       7. The method of  claim 1 , wherein the plastic used to form the piston, vial and retaining cup is selected so that it does not contaminate samples placed in the vial. 
     
     
       8. The method of  claim 1 , wherein the plastic used to form the piston, vial and retaining cup is polypropylene. 
     
     
       9. The method of  claim 1 , further including forming a seal extending outward from the piston adjacent the proximal end of the piston and located to engage and form a fluid tight seal against the interior wall of the vial when the distal end of the piston is placed inside of the vial. 
     
     
       10. The method of  claim 1 , further comprising forming a seal extending outward from the piston adjacent the proximal end of the piston and located to engage and form a fluid tight seal against the interior wall of the vial when the distal end of the piston is placed inside of the vial and adjacent the bottom of the vial. 
     
     
       11. The method of  claim 1 , further comprising placing the cup on the end of the distal end of the piston with the filter between the distal end of the piston and the distal end of the cup. 
     
     
       12. The method of  claim 4 , further comprising placing the cup on the end of the distal end of the piston with the filter between the distal end of the piston and the distal end of the cup. 
     
     
       13. The method of  claim 1 , further comprising forming a cup filter support in the cup and located so that the filter supports the cup and piston abutting the filter when the distal end of the piston is inserted into the cup for use. 
     
     
       14. The method of  claim 13 , wherein the filter supports include radial spokes. 
     
     
       15. The method of  claim 1 , wherein the piston has an inner diameter of about 0.3 inches. 
     
     
       16. A method for assembling a filter vial having a tubular body with a longitudinal axis, a closed bottom, an open top and a cylindrical interior wall joining the bottom, the wall having an internal diameter of D, comprising:
 providing a tubular piston body with opposing distal and proximal ends with an opening in the distal end, the piston having a tubular wall defining an interior of the piston, the piston further having a distal piston flange at or adjacent to the distal end of the piston with the distal piston flange having a portion extending in a radially outward direction from the piston, the tubular wall having an outer diameter less than a diameter D, the piston having a filter support at the distal end of the piston and having openings through which fluid can flow into the interior of the piston during use; 
 providing a retainer cup having a bottom and continuous sidewall with a cylindrical inner surface, the sidewall extending between the bottom at a distal end of the cup and a proximal end of the cup, the cup sidewall having an interior diameter sufficiently smaller than the distal piston flange to allow the sidewall to pass over the distal piston flange with an interference fit, the bottom having an opening through which fluid can flow during use, the cup further having a cup seal extending outward from the proximal end of the cup a distance greater than the diameter D, 
 placing a filter fit inside the cup; and 
 fitting the sidewall of the retainer cup over the distal piston flange so that sidewall of the cup deforms outward as the cup passes over the distal piston flange so the cup sidewall has an outer dimension larger than diameter D at the location of the piston flange when the retainer cup passes over the distal piston flange, the filter being located between the piston filter support and the cup bottom. 
 
     
     
       17. The method of  claim 16 , further comprising the step of placing the bottom of the cup inside the open top of the filter vial and moving the vial and tubular piston until the distal piston flange and cup sidewall deform the wall of the filter vial outward from the longitudinal axis. 
     
     
       18. The method of  claim 17 , wherein a seal extends outward from the piston adjacent the proximal end of the piston, the seal being configured to engage engaging the interior wall of the vial and forming a fluid tight seal against that interior wall when the bottom of the cup is placed inside the filter vial and placed adjacent the closed bottom of the vial.